Clostridium difficile (C. difficile) toxin B is a critical virulence factor that contributes to numerous illnesses. Accordingly, toxin B is a target for diagnosis and vaccination. In particular, since C. difficile is now the leading cause of hospital-acquired illnesses in the world, an abundant supply of toxin B and/or protein fragments of toxin B is needed to develop vaccines and detection systems. However, current protein expression methods and systems do not generate sufficient amounts of toxin B. Thus, there is currently a need for improved systems and methods to express and purify sufficient amounts of recombinant C. difficile toxin B.